Oscillation of Newly Formed Loops After Magnetic Reconnection in the Solar Chromosphere

Abstract

With the high spatial and temporal resolution Hα images from the New Vacuum Solar Telescope, we focus on two groups of loops with an X-shaped configuration in the dynamic chromosphere. We find that the anti-directed loops approach each other and reconnect continually. The connectivity of the loops is changed and new loops are formed and stack together. The stacked loops are sharply bent, implying that they are greatly impacted by the magnetic tension force. When another reconnection process takes place, one new loop is formed and stacks with the previously formed ones. Meanwhile, the stacked loops retract suddenly and move toward the balance position, performing an overshoot movement, which led to an oscillation with an average period of about 45 s. The oscillation of newly formed loops after magnetic reconnection in the chromosphere is observed for the first time. We suggest that the stability of the stacked loops is destroyed due to the attachment of the last new loop and then suddenly retract under the effect of magnetic tension. Because of the retraction, another lower loop is pushed outward and performs an oscillation with a period of about 25 s. The different oscillation periods may be due to their difference in three parameters, i.e., loop length, plasma density, and magnetic field strength.

Quasi-periodic pulsations with multiple periods in hard X-ray emission

“…The period ratios between medium and lower photon energies are much more and complex, since both of them display several dominant periods. Similar as previous findings (Srivastava et al 2008;Inglis & Nakariakov 2009;Su et al 2012;Tian et al 2016;Yang & Xiang 2016), all these period ratios are deviating from two. This may be due to the expansion of flare loop (Verth & Erdélyi 2008), or the density stratification in solar flare (Andries et al 2005).…”

Doppler Shift Oscillations from a Hot Line Observed by IRIS

“…The current discovered oscillatory periods can range from tens of milliseconds (10 −2 s) to thousands of seconds (10 3 s) in the multi-wavelength observations from radio through EUV/UV to X-ray emissions (e.g., Schrijver et al 2002;Inglis & Nakariakov 2009;De Moortel & Nakariakov 2012). And the oscillations within multi-periods have also been detected in the same event (Zimovets & Struminsky 2010;Yang & Xiang 2016;Li et al 2017a).…”

Observation of a Reversal of Breakout Reconnection Preceding a Jet: Evidence of Oscillatory Magnetic Reconnection?

“…The current sheet separates two sets of anti-parallel fieldlines at its two sides as the inflow regions before reconnection, and connects the reconnected fieldlines at its two ends as the outflow region after reconnection. Recently, small current sheets between two sets of anti-parallel loops are reported in several papers Yang & Xiang 2016;Xue et al 2016Xue et al , 2018Yang et al 2018). For the present jet, the existence of C1/C2 indicates the happening of the so-called interchange reconnection between closed field and "open" field (Crooker et al 2002).…”