POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION CURRENT SHEET EVOLUTION A. Bemporad 1, G. Poletto 2, S. T. Suess 3 1 Astronomy & Space Science Dept., University of Firenze, L.go E. Fermi 2, Firenze, Italy 2 INAF - Arcetri Astrophysical Observatory, L.go E. Fermi 5, Firenze, Italy 3 NASA Marshall Space Flight Center, Mailstop SD50, Huntsville, AL, USA

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China Summary: We present here an analysis of the SOHO/UVCS, LASCO, EIT and Ulysses/SWOOPS, SWICS observations of a CME on November 26-27, The talk will be organized as follows: The coronal morphology evolution during and after the CME as seen by LASCO. SOHO/UVCS observations. UVCS data analysis and interpretation. Ulysses/SWOOP & SWICS data. Conclusions.

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China The CME as seen by LASCO: LASCO/C2 (2002/11/26, 00:06  11/29, 23:06 UT) LASCO/C3 (2002/11/26, 00:18  11/29, 22:18 UT) Beginning of UVCS observations

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China SOHO/UVCS observations: Slit position: Latitude: 27°N Height: 1.7 R sun Time interval: 11/26, 18:39  11/29, 02:56 Main spectral lines observed: Fe XVIII l974.9, Fe XV l481.4, Si XII ll , Ca XIV l943.6 O VI ll – , Lyb l1025.7, Lyg l972.5, C III l977.0

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China SOHO - Ulysses quadrature observations: A SOHO – Ulysses quadrature occurs twice a year (  simbols) when the angle between the SOHO Line of Sight (LOS) and the radial from the Sun to Ulysses is ~ 90°. In this geometry, the same plasma studied with remote sensing technique by UVCS is observed later in situ by Ulysses.

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China SOHO: remote sensing observations

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China UVCS data: the “cool” plasma jets SOHO/EIT He II 304 difference images EIT images show recursive ejection of plasma from the Chromosphere at latitudes between ~ 35°N and 55°N. These jets, expected to have a plasma temperature lower than the ~10 6 K Corona, show emission in UVCS data from neutral H (Lyb and Lyg) and the C III ion (T max = 8  10 4 K). Doppler line shifts indicate a plasma v LOS up to 250 km/s. The same jets are also visible in the LASCO/C2 images as an increase in the white light intensity.

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China UVCS data: emission from high temperature plasma Between the latitude of ~ 15°N and 30°N, UVCS data show emission from the Fe XVIII ion (T max ~ 6  10 6 K); the main emission is centered at ~ 23°N (bin #35). Such tempera- tures are unusually high even for Active Regions. At this latitude the Fe XVIII line intensity increases reaching its maximum on November 27, at ~ 14:00 UT (i.e. about 21h after the initiation of the CME), then decreases, while Fe XV intensity increases continuously.

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China UVCS data analysis: plasma temperature determination In coronal conditions, the electron density N e is low enough that the lines form by electron collisional excitation followed by spontaneous emission. The line intensity I line is thus: where n el /n H is the elemental abundance relative to H and n e is the local electron density. G(T e ) is the contribution function defined as: where n ion /n el is the ionic fraction which is a function of the electron temperature T e, B line is the branching ratio for the line transition and q line is the electron excitation rate. The emissivity  can be defined as Fe X, Fe XV and Fe XVIII Emissivities from the CHIANTI spectral code (v. 4.01, computed with the ionization equilibria of Mazzotta et al., 1998). Assuming the ratio between intensities of spectral lines from different ions of the same element to be equal to the ratio between their emissivities; this ratio depends only on the electron temperature T e, hence the observed ratio gives an estimate for T e.

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China UVCS data analysis: temperature at ~ 23°N of latitude In this work T e has been estimated from the observed ratio between the Fe XV and Fe XVIII spectral lines. From this ratio we estimate that, at the beginning of our observations and at a latitude of ~ 23°N, T e was higher than 8.7  10 6 cooling

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China UVCS data: interpretation (from J. Lin et al., 2004, ApJ, 602, 422) CME models predict that, after the eruption of the flux rope (top panel) and the formation of the current sheet below the expanding bubble, magnetic reconnection, starting from the chromospheric level, relaxes the open configuration into a closed. Magnetic reconnection heats plasma converting magnetic energy into kinetic and thermal energies. The heated plasma in the closed loops is expected to cool down via radiative and conductive cooling. Are we looking at the top of the loops or at the Current Sheet?

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China The rising of reconnecting loops: (EIT Fe XII images) v North ≃ 2.3 km/s ; v South ≃ 1.3 km/s If we were looking at the top of a newly reconnecting loop system, we would expect a v rise of ~ 100 km/s.

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China The cooling of reconnecting loops: Order of magnitude estimates of the conductive and radiative cooling time for a semi – circular loop of height of 0.7 R sun shows that the loops cool mainly by conduction over times on the order of 1h. cooling We concluded that we are observing a CURRENT SHEET.

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China Over the past few years UVCS has found evidence of current sheet (see for instance Ko et al. 2003): long lasting, narrow, hot regions were prominent in the Fe XVIII line. A long lasting current sheet in the aftermath of fast CMEs (v 0 flux rope = 1000 km/s) has also been predicted on the basis of theoretical arguments by J. Lin Our Current Sheet last more than 2 days and the CME front speed is about 480 km/s. The Current Sheet and the rising neutral point The rising of the neutral point height p vs time (from J. Lin 2002)

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China Ulysses: in situ observations

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China Ulysses data: the identification for the same hot plasma observed in situ at ~ 4.3 AU. In order to identify the in situ observation interval including the 26 November CME, we made a first extrapolation back to the Sun using the average solar wind speed of 431 km/s. The solar wind speed measured by Ulysses/SWOOPS (Solar Wind Observations Over the Poles of the Sun) Hence, because in general CMEs will slow as they propagate into the interplanetary medium, we assumed that the ICME propagated at half the sum of the average solar wind speed plus the initial speed of the CME from the LASCO/CME list. The 26 November CME is identified as the plasma observed at Ulysses on 14 – 15 December 2002 (DoY 348 – 349). (From G. Poletto, S. T. Suess, A. Bemporad et al., ApJL 2004)

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China The Fe charge state percentage vs day of year in 2002 from Ulysses/SWICS (Solar Wind Ionization state and Composition Spectrometer) In between DoY 348 – 349 (bottom black bar) SWICS observed the highest charge state (Fe 16+ ) reported in the data (top red bars): this could be a benchmark case to relate the in situ freeze-in temperature to temperature of the coronal source wich must have been about 9  10 6 K. Ulysses data: the identification for the same hot plasma observed in situ at ~ 4.3 AU. (From G. Poletto, S. T. Suess, A. Bemporad et al., ApJL 2004)

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China Conclusions: Many cool jets are observed after the CME, not directly correlated with the post – CME evolution. We identified the high temperature plasma as the current sheet following a CME. Lifetime of the current sheet is longer than 2 days. Temperature of the current sheet is higher than of 8.7  10 6 K and decreases in about 2 days down to 3.3  10 6 K. We presented for the first time evidence for the same hot plasma after CME events, in both remote and in situ observations.

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China “Hot” and “cool” plasma distribution In the following evolution the peak of the Fe XVIII emission is located between the two maxima in the O VI emission. At the beginning of the UVCS observations there is very little emission in Fe XVIII and a diffuse emission in O VI. The hot plasma is located in between branches of cool plasma. (From G. Poletto, S. T. Suess, A. Bemporad et al., ApJL 2004)

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China Over the past few years UVCS has found evidence of current sheet in the aftermath of CMEs (Ciaravella et al. 2002; Raymond et al. 2003; Ko et al. 2003): long lasting, narrow, hot regions were prominent in the Fe XVIII line. Rising post CME loops was also observed by SOHO/EIT and Yohkoh/SXT. (not in scale) t cooling ~ 2 hours (T ~ 1.5  10 6 K → 6.0  10 4 K)

POST CME EVENTS: COOL JETS AND CURRENT SHEET EVOLUTION A. Bemporad, G. Poletto, S. T. Suess IAU Symposium 226 Coronal and Stellar Mass Ejections September 13-17, 2004 – Beijing, China