[ITAL]Yohkoh[/ITAL] SXT Observations of X-Ray “Dimming” Associated with a Halo Coronal Mass Ejection

Citations Over TimeTop 10% of 1997 papers

Abstract

A sudden depletion or intensity "dimming" of the X-ray corona sometimes accompanies a solar eruptive flare or coronal mass ejection (CME). We have identified a dimming that occurred just prior to a "halo" CME, observed on 1997 April 7 using the Soft X-ray Telescope (SXT) on Yohkoh. Halo CMEs are prime candidates for "space weather" effects. The dimming occurred in compact regions near a flare of 14 UT on April 7, over a projected area of about 1020 cm-2, and indicate that a mass of a few times 1014 g was ejected. This is a lower limit imposed by the obscuration of the dimming volume by the brightness of the accompanying flare and other factors. Most of the mass deficit comes from two regions close to the ends of a preflare S-shaped active-region structure, and the resulting dimmings in these regions persisted for more than three days following the flare. A cusp-shaped loop—not apparent prior to the flare—dominates the emission in the flare decay phase, and has a mass comparable to that lost in the dimming regions. Our findings are consistent with the source of the CME being a flux rope that erupted, leaving behind the dimming regions. The cusp-shaped loop probably represents magnetic fields reconfigured or reconnected by the eruption. We do not see an X-ray analog of the wavelike disturbance evident in SOHO EUV images.

Related Papers

• → Observations of Double-Periodic X-Ray Emission in Interacting Systems of Solar Flare Loops(2010)34 cited
• → Magnetic Field Evolution Leading to Solar Flares II. Cases with High Magnetic Shear and Flare-Related Shear Change(2000)32 cited
• → Energetics of two-ribbon solar flares(1982)28 cited
• → High resolution observations of white‐light emissions from the opacity minimum during an X‐class flare(2010)3 cited
• → Characteristics of the radio emission of solar white-light flares: Moving type-IV bursts and short-period pulsations associated with post-flare loops(2000)1 cited