Early Chromospheric Early Chromospheric Response During a Response During a

Solar Microflare Solar Microflare Observed with Observed with

RHESSIRHESSI and and SOHOSOHO ’s ’s CDSCDS

Jeffrey W. Brosius (Catholic U at Jeffrey W. Brosius (Catholic U at NASA’s GSFC)NASA’s GSFC)

Gordon D. Holman (NASA’s GSFC)Gordon D. Holman (NASA’s GSFC)

OverviewOverview

We use We use SOHOSOHO/CDS spatially resolved high /CDS spatially resolved high time resolution (7.2 s) EUV spectra that time resolution (7.2 s) EUV spectra that cover a wide temperature range (3×10cover a wide temperature range (3×10⁴ ⁴ – – 8×108×10⁶⁶ K) to investigate a K) to investigate a GOESGOES B1.8 B1.8 microflare.microflare.

Result: O V emission enhancements Result: O V emission enhancements precede those of Fe XIX & 3-12 keV, and O precede those of Fe XIX & 3-12 keV, and O V hasV has

v ~ -200 km/s component for 3 minutes, v ~ -200 km/s component for 3 minutes, with opposing velocities for about 1 minute.with opposing velocities for about 1 minute.

TerminologyTerminology

Chromospheric evaporation: upward motion Chromospheric evaporation: upward motion into the (low density) corona due to expanding into the (low density) corona due to expanding chromospheric material heated by nonthernal chromospheric material heated by nonthernal particle beams and/or thermal conduction.particle beams and/or thermal conduction.

Large energy fluxes produce “explosive” Large energy fluxes produce “explosive” evaporation, which features upward motions in evaporation, which features upward motions in flare (~10 MK) plasma and downward motions flare (~10 MK) plasma and downward motions in cool (~0.1 MK) plasma. Small energy fluxes in cool (~0.1 MK) plasma. Small energy fluxes produce “gentle” evaporation, which features produce “gentle” evaporation, which features only upward motions (Fisher only upward motions (Fisher etet alal. 1985).. 1985).

HistoryHistory Neupert (1968) first described chromospheric Neupert (1968) first described chromospheric

evaporation based on evaporation based on OSO-3OSO-3 and radio and radio observations.observations.

BCS on both BCS on both SMMSMM and and YohkohYohkoh measured measured upflows ~300 km/s in 10 MK lines during flares; upflows ~300 km/s in 10 MK lines during flares; no spatial resolution (Antonucci no spatial resolution (Antonucci etet alal. 1982, . 1982, Mariska Mariska etet alal. 1993).. 1993).

SOHOSOHO/CDS and /CDS and HinodeHinode/EIS raster images yield /EIS raster images yield relative Doppler velocities with time resolution 3 relative Doppler velocities with time resolution 3 min < cadence < 11 min (Czaykowska min < cadence < 11 min (Czaykowska etet alal. . 1999; Teriaca 1999; Teriaca etet alal. 2003; Milligan . 2003; Milligan etet alal. 2006, . 2006, 2008; Raftery 2008; Raftery etet alal. 2009).. 2009).

CDS rapid cadence (~10 s) stare spectra yield CDS rapid cadence (~10 s) stare spectra yield dynamics of flares (Brosius 2003, 2009; Brosius dynamics of flares (Brosius 2003, 2009; Brosius & Phillips 2004; Veronig & Phillips 2004; Veronig etet alal. 2010), a flare-like . 2010), a flare-like transient (Brosius & Holman 2007), and transient (Brosius & Holman 2007), and microflares (Brosius & Holman 2009, 2010).microflares (Brosius & Holman 2009, 2010).

Obtaining Rapid Cadence Obtaining Rapid Cadence (7.2 s) EUV Spectra with (7.2 s) EUV Spectra with

SOHO’SOHO’s CDS: the s CDS: the FLAREDOP StudyFLAREDOP Study

Short exposures (1.5 s).Short exposures (1.5 s). Spatial compression (six 4″×20″ slit Spatial compression (six 4″×20″ slit

pixels).pixels). Limited spectral coverage:Limited spectral coverage:

516-526, 580-611, 623-631 Å.516-526, 580-611, 623-631 Å. Sit & stare; get images elsewhere.Sit & stare; get images elsewhere. Net time resolution is readout-limited to Net time resolution is readout-limited to

7.2 s.7.2 s.

Previous Relative Timing Previous Relative Timing ResultsResults

During During GOESGOES M2.3 flare of 2001 April 24, chromospheric M2.3 flare of 2001 April 24, chromospheric evaporation was “gentle” during precursors and “explosive” during evaporation was “gentle” during precursors and “explosive” during impulsive phase. The Fe XIX intensity rose and stayed above its impulsive phase. The Fe XIX intensity rose and stayed above its preflare noise level during 2preflare noise level during 2ndnd O V precursor, and the Fe XIX O V precursor, and the Fe XIX intensity began its impulsive rise nearly 90 s later than that of the intensity began its impulsive rise nearly 90 s later than that of the cooler lines (Brosius & Phillips 2004, cooler lines (Brosius & Phillips 2004, ApJApJ 613613, 580). , 580).

In FLT during GOES M1.6 flare of 2004 July 22, a slow rise of Fe XIX In FLT during GOES M1.6 flare of 2004 July 22, a slow rise of Fe XIX emission preceded the O V impulsive rise by 2 m, suggesting direct emission preceded the O V impulsive rise by 2 m, suggesting direct coronal heating. Chromospheric evaporation during impulsive coronal heating. Chromospheric evaporation during impulsive phase was “explosive” (Brosius & Holman 2007, phase was “explosive” (Brosius & Holman 2007, ApJApJ 659659, L73)., L73).

Brosius & Holman (2009, Brosius & Holman (2009, ApJApJ 692692, 492) observed gentle evaporation , 492) observed gentle evaporation during a during a GOESGOES B2 microflare on 2005 November 16. The B2 microflare on 2005 November 16. The microflare’s impulsive chromospheric and TR emission began 2.5 m microflare’s impulsive chromospheric and TR emission began 2.5 m before its coronal emission, and 2.8 m before its Fe XIX emission before its coronal emission, and 2.8 m before its Fe XIX emission appeared above the noise.appeared above the noise.

Brosius (2009, Brosius (2009, ApJApJ 701701, 1209) observed conversion from explosive , 1209) observed conversion from explosive to gentle evaporation between successive Fe XIX bursts in an M1.5 to gentle evaporation between successive Fe XIX bursts in an M1.5 flare on 2004 July 27. Initial slow increase of Fe XIX emission may flare on 2004 July 27. Initial slow increase of Fe XIX emission may have been due to direct coronal heating; first O V impulsive rise have been due to direct coronal heating; first O V impulsive rise preceded that of Fe XIX by 1 min.preceded that of Fe XIX by 1 min.

EIT 195 Å and EIT 195 Å and RHESSIRHESSI3-12 keV Images on 2009 3-12 keV Images on 2009

July 5July 5

CDS, CDS, RHESSIRHESSI, , GOESGOES Light Light CurvesCurves

CDS O V 629.7 Å Sample CDS O V 629.7 Å Sample Line Profile Showing Blue Line Profile Showing Blue

ComponentComponent

CDS Line Intensity Ratios CDS Line Intensity Ratios of Blue to Main of Blue to Main

ComponentsComponents

Timings Among Emission Timings Among Emission and Velocity Features in and Velocity Features in

“A”“A”

Timings Among Emission Timings Among Emission and Velocity Features in and Velocity Features in

“B”“B”

SummarySummary Microflare’s onset observed in TR (O V) and Microflare’s onset observed in TR (O V) and

upper chromospheric (He I) emission 1 min upper chromospheric (He I) emission 1 min before Fe XIX and 4 min before 3-12 keV hot before Fe XIX and 4 min before 3-12 keV hot plasma flare emission.plasma flare emission.

In later brightenings O V and He I increased 49 In later brightenings O V and He I increased 49 sec ≤ sec ≤ ΔΔt < 2 min before hot plasma flare t < 2 min before hot plasma flare emissions, which likely indicates heating by emissions, which likely indicates heating by nonthermal particle beam.nonthermal particle beam.

For 3 min during several bursts, O V and He I For 3 min during several bursts, O V and He I profiles had secondary, blueshifted (~ -200 profiles had secondary, blueshifted (~ -200 km/s) components; for ~ 1 min the velocities of km/s) components; for ~ 1 min the velocities of the blueshifted and main components were the blueshifted and main components were opposite, suggesting explosive evaporation.opposite, suggesting explosive evaporation.

No blueshifts in Fe XIX emission.No blueshifts in Fe XIX emission.

AbstractAbstract We observed a We observed a GOESGOES B1.8 microflare in the Sun’s lone AR B1.8 microflare in the Sun’s lone AR

11024 on 2009 July 5 with 11024 on 2009 July 5 with RHESSIRHESSI and and SOHOSOHO’s CDS. CDS ’s CDS. CDS provided rapid cadence (7.2 s) stare spectra within a provided rapid cadence (7.2 s) stare spectra within a narrow FOV toward the region’s center. Emission lines narrow FOV toward the region’s center. Emission lines cover a wide range of temperature, and include He I cover a wide range of temperature, and include He I (<0.025 MK), O V (0.25 MK), Si XII (2 MK), Fe XIX (8 MK). (<0.025 MK), O V (0.25 MK), Si XII (2 MK), Fe XIX (8 MK). The start of initial burst in He I and O V line emission The start of initial burst in He I and O V line emission preceded the emergence of Fe XIX line emission by about 1 preceded the emergence of Fe XIX line emission by about 1 minute, and the emergence of 3-12 keV X-ray emission by minute, and the emergence of 3-12 keV X-ray emission by about 4 minutes. Thus the onset of the flare was observed about 4 minutes. Thus the onset of the flare was observed in upper chromospheric (He I) and transition region (O V) in upper chromospheric (He I) and transition region (O V) line emission before it was detected in high temperature line emission before it was detected in high temperature flare plasma emission. This likely indicates the presence of flare plasma emission. This likely indicates the presence of a nonthermal particle beam early during the microflare. a nonthermal particle beam early during the microflare. Similarly, in subsequent bursts the O V and He I intensities Similarly, in subsequent bursts the O V and He I intensities increase before emissions from the hot flare plasma. In increase before emissions from the hot flare plasma. In intervals lasting up to about 3 minutes during several intervals lasting up to about 3 minutes during several bursts, the He I and O V emission line profiles show bursts, the He I and O V emission line profiles show secondary, highly blueshifted (~ -200 km/s) components; secondary, highly blueshifted (~ -200 km/s) components; during intervals lasting nearly 1 minute the velocities of the during intervals lasting nearly 1 minute the velocities of the primary and secondary components were oppositely primary and secondary components were oppositely directed, suggesting explosive chromospheric evaporation. directed, suggesting explosive chromospheric evaporation. This work was supported by NASA through SR&T grant This work was supported by NASA through SR&T grant NNX07AI09G.NNX07AI09G.

Caption to Figure 1Caption to Figure 1 ((leftleft) 4'×4' EIT 195 Å image obtained at 16:35:17 ) 4'×4' EIT 195 Å image obtained at 16:35:17

UT on 2009 July 5. The position of the CDS slit is UT on 2009 July 5. The position of the CDS slit is outlined as six 4″×20″ segments into which its outlined as six 4″×20″ segments into which its spatially resolved spectra were binned, centered spatially resolved spectra were binned, centered around its commanded pointing at (+119″.8, -around its commanded pointing at (+119″.8, -458″.2). The ≈10″ uncertainty in the CDS 458″.2). The ≈10″ uncertainty in the CDS pointing is overplotted as a dotted rectangle. pointing is overplotted as a dotted rectangle.

((rightright) 1'×1' ) 1'×1' RHESSIRHESSI 3-12 keV image averaged 3-12 keV image averaged over the 1-min time interval 16:36-16:37 UT. The over the 1-min time interval 16:36-16:37 UT. The CDS slit (and uncertainty) is again overplotted. CDS slit (and uncertainty) is again overplotted. RHESSIRHESSI contour levels correspond to 10, 30, 50, contour levels correspond to 10, 30, 50, and 70% of the maximum count rate in the and 70% of the maximum count rate in the RHESSIRHESSI image cube. The microflare was observed image cube. The microflare was observed in slit pixels “A” and “B.”in slit pixels “A” and “B.”

Caption to Figure 2Caption to Figure 2

EUV light curves from CDS in “A,” along EUV light curves from CDS in “A,” along with with GOESGOES 1-8 Å and 1-8 Å and RHESSIRHESSI 3-12 keV light 3-12 keV light curves. Fe XIX is smoothed with a 9-point curves. Fe XIX is smoothed with a 9-point running boxcar, and plotted on an absolute running boxcar, and plotted on an absolute intensity scale; all other light curves are on intensity scale; all other light curves are on arbitrary scales. Solid vertical lines indicate arbitrary scales. Solid vertical lines indicate a relatively quiescent interval (15:20-15:40 a relatively quiescent interval (15:20-15:40 UT) from which “reference” quantities UT) from which “reference” quantities (including wavelengths common to “A” & (including wavelengths common to “A” & “B”) are derived. Note that the B1.4 and “B”) are derived. Note that the B1.4 and B1.8 microflares appear blended together B1.8 microflares appear blended together when viewed in Si XII line emission.when viewed in Si XII line emission.

Caption to Figure 3Caption to Figure 3

Sample profile of O V 629.7 Å (spectral Sample profile of O V 629.7 Å (spectral intensity in ergs cmˉ² sˉ¹ srˉ¹ Åˉ¹ intensity in ergs cmˉ² sˉ¹ srˉ¹ Åˉ¹ vsvs. wavelength . wavelength in Å) in “A” at 16:38:45 UT during the rapid rise in Å) in “A” at 16:38:45 UT during the rapid rise of the secondary blueshifted component. The of the secondary blueshifted component. The observed profile is displayed as asterisks, the observed profile is displayed as asterisks, the “main” and “blueshifted” components are “main” and “blueshifted” components are displayed as solid white and blue curves, and displayed as solid white and blue curves, and the net fitted profile is a solid red curve. Dotted the net fitted profile is a solid red curve. Dotted vertical lines indicate ±3vertical lines indicate ±3σσ from the reference from the reference wavelength. Short solid vertical lines indicate wavelength. Short solid vertical lines indicate the centroid wavelengths of the main and the centroid wavelengths of the main and blueshifted components, for which the blueshifted components, for which the corresponding velocities are given in the upper corresponding velocities are given in the upper left.left.

Caption to Figure 4Caption to Figure 4

Intensity ratio of the secondary, blueshifted Intensity ratio of the secondary, blueshifted component to the main component for O V, He component to the main component for O V, He I, and Si XII in “A”. Horizontal lines indicate I, and Si XII in “A”. Horizontal lines indicate 22σσ above the average ratios derived in the above the average ratios derived in the “reference” interval (15:20-15:40 UT) during “reference” interval (15:20-15:40 UT) during which the secondary component is considered which the secondary component is considered to be noise. Time intervals during which we to be noise. Time intervals during which we find significant, secondary, blueshifted O V find significant, secondary, blueshifted O V components are 16:35:40-16:36:30 and components are 16:35:40-16:36:30 and 16:38:14-16:41:27 UT in “A” and 16:35:40-16:38:14-16:41:27 UT in “A” and 16:35:40-16:37:31 and 16:38:14-16:40:03 UT in “B”.16:37:31 and 16:38:14-16:40:03 UT in “B”.

Caption to Figure 5Caption to Figure 5

Normalized light curves (left) and relative Doppler Normalized light curves (left) and relative Doppler velocities (right) in “A”. For intervals in which two velocities (right) in “A”. For intervals in which two components are observed, the displayed intensity is the components are observed, the displayed intensity is the sum of the primary and secondary components, and the sum of the primary and secondary components, and the velocity of the blueshifted component is divided by 5 to velocity of the blueshifted component is divided by 5 to reduce the vertical plot range. Start times for various reduce the vertical plot range. Start times for various events are indicated with solid vertical lines, including events are indicated with solid vertical lines, including (a) the start of the O V precursor burst at 16:26:02 UT, (a) the start of the O V precursor burst at 16:26:02 UT, (b) start of the Fe XIX intensity increase at 16:26:46, (b) start of the Fe XIX intensity increase at 16:26:46, (c) start of the 3-12 keV emission at 16:30:10, (d) start (c) start of the 3-12 keV emission at 16:30:10, (d) start of the rapid O V intensity increase at 16:34:37, (f) Fe of the rapid O V intensity increase at 16:34:37, (f) Fe XIX between-burst minimum at 16:35:26, (g) start of a XIX between-burst minimum at 16:35:26, (g) start of a later rapid O V intensity increase at 16:38:14, (h) Fe later rapid O V intensity increase at 16:38:14, (h) Fe XIX rapid intensity rise to the main phase plateau at XIX rapid intensity rise to the main phase plateau at 16:40:10 UT.16:40:10 UT.

Caption to Figure 6Caption to Figure 6 Normalized light curves (left) and relative Doppler Normalized light curves (left) and relative Doppler

velocities (right) in “B”. For intervals in which two velocities (right) in “B”. For intervals in which two components are observed, the displayed intensity is the components are observed, the displayed intensity is the sum of the primary and secondary components, and the sum of the primary and secondary components, and the velocity of the blueshifted component is divided by 5 to velocity of the blueshifted component is divided by 5 to reduce the vertical plot range. Start times for various reduce the vertical plot range. Start times for various events are indicated with solid vertical lines, including events are indicated with solid vertical lines, including (m) the start of the O V precursor burst at 16:26:09 UT, (m) the start of the O V precursor burst at 16:26:09 UT, (n) start of the Fe XIX intensity increase at 16:29:14, (c) (n) start of the Fe XIX intensity increase at 16:29:14, (c) start of the 3-12 keV emission at 16:30:10, (d) start of start of the 3-12 keV emission at 16:30:10, (d) start of the rapid O V intensity increase at 16:34:37, (o) Fe XIX the rapid O V intensity increase at 16:34:37, (o) Fe XIX between-burst minimum at 16:36:15, (g) start of a later between-burst minimum at 16:36:15, (g) start of a later rapid O V intensity increase at 16:38:14, (p) Fe XIX rapid O V intensity increase at 16:38:14, (p) Fe XIX rapid intensity rise to the main phase plateau at rapid intensity rise to the main phase plateau at 16:39:28 UT. For 16:36:45-16:37:31 and 16:39:08-16:39:28 UT. For 16:36:45-16:37:31 and 16:39:08-16:40:03 UT the main O V component is redshifted 16:40:03 UT the main O V component is redshifted while the secondary component is blueshifted, while the secondary component is blueshifted, suggesting explosive evaporation.suggesting explosive evaporation.

Microflare of 2005 Microflare of 2005 November 16November 16

CDS light curves of He I (/1.5), Si CDS light curves of He I (/1.5), Si XII (×7), O V, Fe XIX (×10).XII (×7), O V, Fe XIX (×10).

Two precursors before microflare, Two precursors before microflare, with enhancement factors 1.3, 1.7 with enhancement factors 1.3, 1.7 (He I), & 2.4, 3.8 (O V).(He I), & 2.4, 3.8 (O V).

Chromospheric & transition Chromospheric & transition region emission increase first, region emission increase first, indicating nonthermal electrons.indicating nonthermal electrons.

20 s impulsive EUV burst during 20 s impulsive EUV burst during which Fe XIX starts increase.which Fe XIX starts increase.

Burst enhancement factors: 3.2 Burst enhancement factors: 3.2 for He I, 11 for O V, 2.0 for Si XII; for He I, 11 for O V, 2.0 for Si XII; 24 for O III, 2.4 for 1600 Å.24 for O III, 2.4 for 1600 Å.

Fe XIX (and GOES 1-8 Å) emission Fe XIX (and GOES 1-8 Å) emission lasts only about 2 minutes.lasts only about 2 minutes.

Gentle chromospheric Gentle chromospheric evaporation, with upward evaporation, with upward velocities about -20 km/s.velocities about -20 km/s.

TRACE TRACE 195195 Å Images With Å Images With Part of CDS Slit in 27 July Part of CDS Slit in 27 July

2004 M1.5 Flare2004 M1.5 Flare

Fig. 1: MDI Fig. 1: MDI Magnetogram andMagnetogram andEIT 195 Å ImageEIT 195 Å Image

Caption to Figure 1Caption to Figure 1 4'×4' (a) MDI magnetogram and (b) EIT 4'×4' (a) MDI magnetogram and (b) EIT

195 Å image obtained at the times 195 Å image obtained at the times indicated in each frame on 2009 July 5. indicated in each frame on 2009 July 5. The position of the CDS slit is outlined as The position of the CDS slit is outlined as six 4″×20″ segments into which its six 4″×20″ segments into which its spatially resolved spectra were binned, spatially resolved spectra were binned, centered around its commanded pointing centered around its commanded pointing at (+119″.8, -458″.2). The ≈10″ at (+119″.8, -458″.2). The ≈10″ uncertainty in the CDS pointing is uncertainty in the CDS pointing is overplotted as a dotted rectangle. The overplotted as a dotted rectangle. The microflare was observed in slit pixels “A” microflare was observed in slit pixels “A” and “B,” indicated in (b).and “B,” indicated in (b).

Figure 2: CDS, Figure 2: CDS, RHESSIRHESSI, , GOESGOES Light Curves Light Curves

Caption to Figure 2Caption to Figure 2

EUV light curves from CDS in “A” and EUV light curves from CDS in “A” and “B”, along with “B”, along with GOESGOES 1-8 Å and 1-8 Å and RHESSIRHESSI 3-12 keV light curves. Fe XIX is 3-12 keV light curves. Fe XIX is smoothed with a 9-point running boxcar, smoothed with a 9-point running boxcar, and plotted on an absolute intensity and plotted on an absolute intensity scale; all other light curves are on scale; all other light curves are on arbitrary scales. The solid vertical lines arbitrary scales. The solid vertical lines near the beginning of both frames near the beginning of both frames indicate a relatively quiescent interval indicate a relatively quiescent interval (15:20-15:40 UT) from which “reference” (15:20-15:40 UT) from which “reference” quantities (including wavelengths quantities (including wavelengths common to both frames) are derived.common to both frames) are derived.

FigureFigure 3:3: RHESSI RHESSI Images Images of Two Microflare of Two Microflare

BrighteningsBrightenings

Caption to Figure 3Caption to Figure 3

RHESSIRHESSI 3-12 keV images showing two 3-12 keV images showing two bursts during the microflare. The 1-min bursts during the microflare. The 1-min time interval for each image is indicated in time interval for each image is indicated in the upper right. “Before” frames are on the upper right. “Before” frames are on the left, and “during” on the right. The the left, and “during” on the right. The CDS slit (and uncertainty) is overplotted as CDS slit (and uncertainty) is overplotted as in Fig. 1. Contour levels are the same in in Fig. 1. Contour levels are the same in all frames, and correspond to 10, 30, 50, all frames, and correspond to 10, 30, 50, and 70% of the maximum count rate in the and 70% of the maximum count rate in the RHESSIRHESSI image cube. All images are image cube. All images are displayed on the same brigtness scale.displayed on the same brigtness scale.

Fig. 4: CDS O V 629.7 Å Fig. 4: CDS O V 629.7 Å Line Profiles Showing Rise Line Profiles Showing Rise

of Blue Componentof Blue Component

Caption to Figure 4Caption to Figure 4 Sequence of O V 629.7 Å profiles (spectral Sequence of O V 629.7 Å profiles (spectral

intensity in ergs cmˉ² sˉ¹ srˉ¹ Åˉ¹ intensity in ergs cmˉ² sˉ¹ srˉ¹ Åˉ¹ vsvs. wavelength . wavelength in Å) showing the rapid rise of the secondary in Å) showing the rapid rise of the secondary blueshifted component from 16:38:14 to blueshifted component from 16:38:14 to 16:39:00 UT in “A”. The central time of each 16:39:00 UT in “A”. The central time of each exposure is indicated in the upper left. The exposure is indicated in the upper left. The observed profile is displayed as asterisks, the observed profile is displayed as asterisks, the “main” and “blueshifted” components are “main” and “blueshifted” components are displayed as solid white and blue curves, displayed as solid white and blue curves, respectively, and the net fitted profile is a solid respectively, and the net fitted profile is a solid red curve. Dotted vertical lines indicate ±3red curve. Dotted vertical lines indicate ±3σσ from the reference wavelength. Short solid from the reference wavelength. Short solid vertical lines indicate the centroid wavelengths vertical lines indicate the centroid wavelengths of the main and blueshifted components, for of the main and blueshifted components, for which the corresponding velocities are given in which the corresponding velocities are given in the upper left of each frame.the upper left of each frame.

Figure 5: CDS Line Figure 5: CDS Line Intensity Ratios of Blue to Intensity Ratios of Blue to

Main ComponentsMain Components

Caption to Figure 5Caption to Figure 5

Intensity ratio of the secondary, blueshifted Intensity ratio of the secondary, blueshifted component to the main component for O V, He component to the main component for O V, He I, and Si XII in “A” and “B”. Horizontal lines I, and Si XII in “A” and “B”. Horizontal lines indicate 2indicate 2σσ above the average ratios derived in above the average ratios derived in the “reference” interval (15:20-15:40 UT) the “reference” interval (15:20-15:40 UT) during which the secondary component is during which the secondary component is considered to be noise. Time intervals during considered to be noise. Time intervals during which we find significant, secondary, which we find significant, secondary, blueshifted O V components are 16:35:40-blueshifted O V components are 16:35:40-16:36:30 and 16:38:14-16:41:27 UT in “A” and 16:36:30 and 16:38:14-16:41:27 UT in “A” and 16:35:40-16:37:31 and 16:38:14-16:40:03 UT in 16:35:40-16:37:31 and 16:38:14-16:40:03 UT in “B”.“B”.

Figure 6: Timings Among Figure 6: Timings Among Emission and Velocity Emission and Velocity

Features in “A”Features in “A”

Caption to Figure 6Caption to Figure 6

Normalized light curves (left) and relative Doppler Normalized light curves (left) and relative Doppler velocities (right) in “A”. For intervals in which two velocities (right) in “A”. For intervals in which two components are observed, the displayed intensity is the components are observed, the displayed intensity is the sum of the primary and secondary components, and the sum of the primary and secondary components, and the velocity of the blueshifted component is divided by 5 to velocity of the blueshifted component is divided by 5 to reduce the vertical plot range. Start times for various reduce the vertical plot range. Start times for various events are indicated with solid vertical lines, including events are indicated with solid vertical lines, including (a) the start of the O V precursor burst at 16:26:02 UT, (a) the start of the O V precursor burst at 16:26:02 UT, (b) start of the Fe XIX intensity increase at 16:26:46, (b) start of the Fe XIX intensity increase at 16:26:46, (c) start of the 3-12 keV emission at 16:30:10, (d) start (c) start of the 3-12 keV emission at 16:30:10, (d) start of the rapid O V intensity increase at 16:34:37, (f) Fe of the rapid O V intensity increase at 16:34:37, (f) Fe XIX between-burst minimum at 16:35:26, (g) start of a XIX between-burst minimum at 16:35:26, (g) start of a later rapid O V intensity increase at 16:38:14, (h) Fe later rapid O V intensity increase at 16:38:14, (h) Fe XIX rapid intensity rise to the main phase plateau at XIX rapid intensity rise to the main phase plateau at 16:40:10 UT.16:40:10 UT.

Figure 7: Timings Among Figure 7: Timings Among Emission and Velocity Emission and Velocity

Features in “B”Features in “B”

Caption to Figure 7Caption to Figure 7 Normalized light curves (left) and relative Doppler Normalized light curves (left) and relative Doppler

velocities (right) in “B”. For intervals in which two velocities (right) in “B”. For intervals in which two components are observed, the displayed intensity is the components are observed, the displayed intensity is the sum of the primary and secondary components, and the sum of the primary and secondary components, and the velocity of the blueshifted component is divided by 5 to velocity of the blueshifted component is divided by 5 to reduce the vertical plot range. Start times for various reduce the vertical plot range. Start times for various events are indicated with solid vertical lines, including events are indicated with solid vertical lines, including (m) the start of the O V precursor burst at 16:26:09 UT, (m) the start of the O V precursor burst at 16:26:09 UT, (n) start of the Fe XIX intensity increase at 16:29:14, (c) (n) start of the Fe XIX intensity increase at 16:29:14, (c) start of the 3-12 keV emission at 16:30:10, (d) start of start of the 3-12 keV emission at 16:30:10, (d) start of the rapid O V intensity increase at 16:34:37, (o) Fe XIX the rapid O V intensity increase at 16:34:37, (o) Fe XIX between-burst minimum at 16:36:15, (g) start of a later between-burst minimum at 16:36:15, (g) start of a later rapid O V intensity increase at 16:38:14, (p) Fe XIX rapid O V intensity increase at 16:38:14, (p) Fe XIX rapid intensity rise to the main phase plateau at rapid intensity rise to the main phase plateau at 16:39:28 UT. For 16:36:45-16:37:31 and 16:39:08-16:39:28 UT. For 16:36:45-16:37:31 and 16:39:08-16:40:03 UT the main O V component is redshifted 16:40:03 UT the main O V component is redshifted while the secondary component is blueshifted, while the secondary component is blueshifted, suggesting explosive evaporation.suggesting explosive evaporation.

SummarySummary Microflare’s onset observed in TR (O V) and Microflare’s onset observed in TR (O V) and

upper chromospheric (He I) emission 1 min upper chromospheric (He I) emission 1 min before Fe XIX and 4 min before 3-12 keV hot before Fe XIX and 4 min before 3-12 keV hot plasma flare emission.plasma flare emission.

In later brightenings O V and He I increased 49 In later brightenings O V and He I increased 49 sec ≤ sec ≤ ΔΔt < 2 min before hot plasma flare t < 2 min before hot plasma flare emissions, which likely indicates heating by emissions, which likely indicates heating by nonthermal particle beam.nonthermal particle beam.

For 3 min during several bursts, O V and He I For 3 min during several bursts, O V and He I profiles had secondary, blueshifted (~ -200 profiles had secondary, blueshifted (~ -200 km/s) components; for ~ 1 min the velocities of km/s) components; for ~ 1 min the velocities of the blueshifted and main components were the blueshifted and main components were opposite, suggesting explosive evaporation.opposite, suggesting explosive evaporation.

No blueshifts in Fe XIX or Si XII emission.No blueshifts in Fe XIX or Si XII emission.