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Alphonse C Sterling

Publications and source records attributed to Alphonse C Sterling.

34 records · Page 2
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Another Look at Erupting Minifilaments at the Base of Solar X-Ray Polar Coronal “Standard” and “Blowout” Jets

We examine 21 solar polar coronal jets that we identify in soft X-ray images obtained fromthe Hinode/X-ray telescope (XRT). We identify 11 of these jets as blowout jets and four asstandard jets (with six uncertain), based on their X-ray-spire widths being respectively wide or narrow (compared to the jet’s base) in the XRT images. From corresponding Extreme Ultraviolet (EUV) images from the Solar Dynamics Observatory’s (SDO) Atmospheric Imaging Assembly (AIA), essentially all (at least 20 of 21) of the jets are made by minifilament eruptions, consistent with other recent studies. Here, we examine the detailed nature of the erupting minifilaments (EMFs) in the jet bases. Wide-spire (“blowout”) jets often have ejective EMFs, but sometimes they instead have an EMF that is mostly confined to the jet’s base rather than ejected. We also demonstrate that narrow-spire (“standard”) jets can have either a confined EMF, or a partially confined EMF where some of the cool minifilament leaks into the jet’s spire. Regarding EMF visibility: we find that in some cases the minifilament is apparent in as few as one of the four EUV channels we examined, being essentially invisible in the other channels; thus it is necessary to examine images from multiple EUV channels before concluding that a jet does not have an EMF at its base. The size of the EMFs, measured projected against the sky and early in their eruption, is 14′′ ± 7′′, which is within a factor of two of other measured sizes of coronal-jet EMFs. A full report on these results are available in Sterling et al. (2022, ApJ, 927, 127).This work was supported by NASA’s HGI and HSR programs, and by the MSFC HinodeProject.

Alphonse C Sterling↗
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On the Onset Mechanism for Solar Coronal Jets, and Implications for the Onset Mechanism for CME-Producing Eruptions

Large-scale solar eruptions often include ejection of a filament, a solar flare, and expulsion of a coronal mass ejection (CME). Unravelling the magnetic processes that build up the free energy for these eruptions and trigger that energy's release in the eruption is a continuing challenge in solar physics. Such large-scale eruptions are comparatively infrequent, with the moderate level ones (say, GOES M-class events) occurring perhaps once every few days on average during active-activity times, and much less frequently during quieter times. In contrast, solar coronal jets, which are long (~50,000 km), narrow (<~10,000 km), transient (~10---20 min) plasma spires with bright bases and that are seen in soft X-rays and EUV, occur much more frequently, likely several hundred times per day independent of large-scale solar activity level. Recent studies indicate that coronal jets are small-scale versions of large-scale eruptions, often produced by eruption of a small-scale "miniflament," that results in a "miniflare" analogous to a larger typical solar flare, and that sometimes produces a CME analogue (a "narrow CME" or "white-light jet"). Under the assumption that jets are small-scale eruptions, their higher occurrence frequency and faster build-up evolution reveals perhaps fundamental aspects of all eruptions that are not as easy to discern in the more-complex magnetic environment and the slower build up to the larger eruptions. Therefore, the study of coronal jets can provide insights into the onset mechanism of CME-producing large-scale eruptions.

Alphonse C Sterling↗