Coronal Responses to Explosive Events Adria C. Updike Smith College / Harvard-Smithsonian Center for Astrophysics Amy Winebarger and Kathy Reeves, Center for Astrophysics

MDI photosphere T = 5800 K EIT 304 Å T = – K EIT 195Å T = 1.5 million K EIT 171Å T = 1 million K

Coronal Heating insert graphic from mariska book

Coronal Heating Solar Surface = 5800 K Chromosphere = K Transition Region Corona = 10 6 K Ruled out: Radiation Convection

Coronal Heating Insert magnetic reconnection graphic Explosive Events to ergs ~2,000 km Large Solar Flares to ergs ~10 Mm This image of coronal loops over the eastern limb of the Sun was taken in the TRACE 171 Å pass band, characteristic of plasma at 1 MK, on November 6, 1999, at 02:30 UT. The image was rotated over +90 degrees.

Explosive Events to ergs ~2,000 km occur in Transition Region at 100,000 K heated to coronal temperatures?

TRACE Transition Region and Coronal Explorer Observes 171 Å, 195 Å, 284 Å, 1600 Å, 1550 Å, and 1216 Å.

images taken May 13, Å 171 Å near temperature minimum 10 4 K near temperature maximum 10 6 K

SUMER Solar Ultraviolet Measurements of Emitted Radiation Insert SUMER spectra from movie Observed in the C IV line at 1548 Å and in the Ne VIII line at 1540 Å. Data set from May 13, 1999 from 13:1:14.47 UT to 13:33:6.0 UT

Insert SUMER spectra

Selection Criteria profiles with greater than 500 counts average width of C IV profile = 3.3 pixels 2 ± 0.4 pixels 2 average width of Ne VIII profile = 4.0 pixels 2 ± 0.5 pixels 2 A statistically significant event has greater than 500 counts and is 3 σ above either average skewness or average width. Number of Events C IVNe VIII chosen greater than 3 δ width32294 greater than 3 δ skew with positive skew78180 with negative skew937335

TRACE movie The line moving across the TRACE images marks the position of the SUMER slit at the displayed time. The time is the difference in the SUMER slit time and the time of the first TRACE image.

C IV contour map High skewness in green, high width in red. Created by smoothing over original contour maps. Areas of SUMER events plotted on TRACE images. Areas of high skewness tend to follow the coronal loop, while the high width is concentrated at the foot points.

Ne VIII contour map The high skewness is represented by light blue, and the high width is yellow. The Ne VIII follows the magnetic foot points more closely than the C IV map did.

Light Curves We selected a small contoured area from the figure below and averaged the number of counts in this area as a function of time. Area one: x 1 = 329 x 2 = 331 y 1 = 139 y 2 = 140 Area two: x 1 = 305 x 2 = 308 y 1 = 137 y 2 = 140 Area three: x 1 = 310 x 2 = 312 y 1 = 58 y 2 = 60 Area four: x 1 = 280 x 2 = 282 y 1 = 70 y 2 = 72

Light Curves Four light curves from TRACE 171 Å data, May 13, DN/s. The error is DN/sqrt(11).

Light Curves To quantify our results, we compared the maximum short term (<5 min) fluctuation in TRACE pixels above event regions to “normal” fluctuations observed over areas that did not show explosive event characteristics during the SUMER scan. The fluctuation is defined as the difference between the minimum and maximum points on the light curve.

Global Birthrate number of new events occurring each second N o = number of observed events τ = total observation time A sun = surface area of the sun that can be considered an active region A slit = deprojected area of SUMER slit on sun C IV 2108 events s -1 Ne VIII 335 events s -1 Previous Results: 753 events s -1 (Brueckner and Bartoe) 600 events s -1 (Dere, Brueckner and Bartoe)

Conclusions We found that the typical fluctuation for both events and non-events is ~ 1.5 DN/s. However, while the non-events became nearly non-existant after a fluctuation of 2.5 DN/s, the events continued out to more than 20 DN/s. This indicates a great amount of activity taking place in the regions identified as events. By constraining our time scale to 5 minutes, we determined that 35% of our events had greater than 3 σ above non-events. We witnessed a coronal response in TRACE to an explosive event in SUMER 35% of the time. Explosive events can contribute 10% of the energy required to heat the solar corona. It is not clear whether the explosive events are directly related to the coronal response, or if they are both separate responses to reconnection.