Early EVE Observations and Flare First Results Frank Eparvier, EVE Project Scientist University of Colorado – LASP

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 nm and broadbands shortward of 27 nm  15 observations per day (3 min out of every 96 min) 2

EVE is the EUV Variability Experiment on SDO an irradiance instrument with significant improvements in spectral resolution and time coverage Channel Range tt MEGS-A16-18 nm0.1 nm10 sec MEGS-A nm0.1 nm10 sec MEGS-B nm0.1 nm10 sec MEGS-SAM0.1-7 nm(1 nm)10 sec MEGS-P121.6 nm1 nm0.25 s ESP nm4 nm0.25 s But Now We Have EVE! EVE

Sample Spectrum from MEGS 4

“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

EVE Has Observed Lots of Flares! 6 X-class: 0 M-class: 4 C-class: 35 B-class: 300+

Main Flare Timing Depends on Temperature 7 Thermal Phase (hot lines) Impulsive Phase (cool lines) Cooling Single Reconnection Event M2.0 Compact Flare

…and on Type of Flare 8 Thermal Phase Drawn out Impulsive Phase Cooling Multiple Cascading Reconnection M1.0 Two-Ribbon Flare

EVE Post-Flare Response After some flares some EUV lines show significant fluctuations hours after the main flare. 9

EVE Post-Flare Response Other lines show dimming, or no later response. 10

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) 11

EUV Spectral Variability of a Flare 12

Late Phase Q EUV Variations nm Late Phase

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 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 14

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) 15

AIA 335 Channel