Early EVE Observations and Flare First Results

Frank Eparvier, EVE Project ScientistUniversity of Colorado – LASPeparvier@colorado.edu303-492-4546

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Contributions Due to TIMED-SEE SEE pointed out that a single proxy

doesn’t work for all EUV spectral variability

SEE allowed us to create better proxy models of spectral variability on SC, rotational, and daily scales (e.g. FISM) using multiple proxies (4)

SEE gave us a first, tantalizing glimpse at flare variability in the EUV FISM modeled flare variability based

on GOES 1-8 Å (and its time derivative)

But SEE was spectrally and temporally limited 0.4 nm resolution for 27-194 nm and

broadbands shortward of 27 nm 15 observations per day (3 min out of

every 96 min)

EVE is the EUV Variability Experiment on SDOan irradiance instrument with significant improvements in spectral

resolution and time coverage

Channel l Range Dl Dt

MEGS-A1 6-18 nm 0.1 nm 10 sec

MEGS-A2 18-37 nm 0.1 nm 10 sec

MEGS-B 37-106 nm 0.1 nm 10 sec

MEGS-SAM 0.1-7 nm (1 nm) 10 sec

MEGS-P 121.6 nm 1 nm 0.25 s

ESP 0.1-38 nm 4 nm 0.25 s

But Now We Have EVE!

EVE

http://lasp.colorado.edu/eve

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Sample Spectrum from MEGS

“Quiet” Sun Fluctuations EVE sees 5-10% “pulsing” fluctuations in EUV lines when an active region is

on the disk. These have ~4-6 hour periodicity and are related to small flares below the GOES XRS ability to detect. But not beyond EVE ability!

“Quiet” Period

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EVE Has Observed Lots of Flares!

X-class: 0M-class: 4C-class: 35B-class: 300+

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Main Flare Timing Depends on Temperature

Thermal Phase (hot lines)

Impulsive Phase (cool lines)

Cooling

Single Reconnection EventM2.0 Compact Flare

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…and on Type of Flare

Thermal Phase

Drawn out Impulsive Phase

Cooling

Multiple Cascading ReconnectionM1.0 Two-Ribbon Flare

EVE Post-Flare Response

After some flares some EUV lines show significant fluctuations hours after the main flare.

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EVE Post-Flare Response

Other lines show dimming, or no later response.

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Which Flares Have Late Phases?

EVE observed 21 flares of C-Class or larger in May – August 2010 period (C1 to M2)

9 of these flares showed a “late phase” All flares with late phases were compact and

eruptive Developing new categorization of flares based

on EUV behavior (coronal dimming and late phases)

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EUV Spectral Variability of a Flare

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Late Phase QEUV Variations

0-45 nm

Late Phase

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What Are We Learning from EVE?

There are significant variations due to flares that aren’t captured by GOES XRS as a proxy

Small flares (A-Class) cause 5-10% EUV variability through the days when active regions are on the disk (and GOES XRS is flat)

The main flare peak varies in time for different EUV lines as a function of emission temperature

Some EUV lines (e.g. 17.1 nm) dim during flares Some flares have a “Late Phase” an hour or

more after the main flare with large increases in some EUV lines

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More to Come

Fall AGU 2010: Three SDO-specific sessions Other SDO-related sessions (e.g. Geospace impacts)

“Science” papers being prepared by SDO teams LWS-SDO-1 Conference: ~May 3-6, 2011 in

Lake Tahoe (announcement soon)

AIA 335 Channel