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Energy and helicity budgets of solar quiet regions  

Kostas Tziotziou   Submitted: 2014-03-05 01:28

We investigate the free magnetic energy and relative magnetic helicity budgets of solar quiet regions. Using a novel non-linear force-free method requiring single solar vector magnetograms we calculate the instantaneous free magnetic energy and relative magnetic helicity budgets in 55 quiet-Sun vector magnetograms. As in a previous work on active regions, we construct here for the first time the (free) energy-(relative) helicity diagram of quiet-Sun regions. We find that quiet-Sun regions have no dominant sense of helicity and show monotonic correlations a) between free magnetic energy/relative helicity and magnetic network area and, consequently, b) between free magnetic energy and helicity. Free magnetic energy budgets of quiet-Sun regions represent a rather continuous extension of respective active-region budgets towards lower values, but the corresponding helicity transition is discontinuous due to the incoherence of the helicity sense contrary to active regions. We further estimate the instantaneous free magnetic-energy and relative magnetic-helicity budgets of the entire quiet Sun, as well as the respective budgets over an entire solar cycle. Derived instantaneous free magnetic energy budgets and, to a lesser extent, relative magnetic helicity budgets over the entire quiet Sun are comparable to the respective budgets of a sizeable active region, while total budgets within a solar cycle are found higher than previously reported. Free-energy budgets are comparable to the energy needed to power fine-scale structures residing at the network, such as mottles and spicules.

Authors: Tziotziou, K., Tsiropoula, G., Georgoulis, M.K., Kontogiannis, I.
Projects: Dutch Open Telescope,Hinode/SOT

Publication Status: A&A (in press)
Last Modified: 2014-03-05 12:25
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Magnetic Energy and Helicity Budgets in NOAA AR 11158  

Kostas Tziotziou   Submitted: 2013-06-11 01:18

In previous works we introduced a nonlinear force-free method that self-consistently calculates the instantaneous budgets of free magnetic energy and relative magnetic helicity in solar active regions (ARs). Calculation is expedient and practical, using only a single vector magnetogram per computation. We apply this method to a timeseries of 600 high-cadence vector magnetograms of the eruptive NOAA AR 11158 acquired by the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory over a five-day observing interval. Besides testing our method extensively, we use it to interpret the dynamical evolution in the AR, including eruptions. We find that the AR builds large budgets of both free magnetic energy and relative magnetic helicity, sufficient to power many more eruptions than the ones it gave within the interval of interest. For each of these major eruptions, we find eruption-related decreases and subsequent free-energy and helicity budgets that are consistent with the observed eruption (flare and coronal-mass-ejection [CME]) sizes. In addition, we find that (1) evolution in the AR is consistent with the recently proposed (free) energy - (relative) helicity diagram of solar ARs, (2) eruption-related decreases occur {it before} the flare and the projected CME-launch times, suggesting that CME progenitors precede flares, and (3) self-terms of free energy and relative helicity most likely originate from respective mutual-terms, following a progressive mutual-to-self conversion pattern that most likely stems from magnetic reconnection. This results in the non-ideal formation of increasingly helical pre-eruption structures and instigates further research on the triggering of solar eruptions with magnetic helicity firmly placed in the eruption cadre.

Authors: Kostas Tziotziou, Manolis K. Georgoulis, Yang Liu
Projects: SDO-HMI

Publication Status: ApJ (in press)
Last Modified: 2013-06-11 11:31
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The Magnetic Energy - Helicity Diagram of Solar Active Regions  

Kostas Tziotziou   Submitted: 2012-09-26 02:49

Using a recently proposed nonlinear force-free method designed for single vector magnetograms of solar active regions we calculate the instantaneous free magnetic energy and relative magnetic helicity budgets in 162 vector magnetograms corresponding to 42 different active regions. We find a statistically robust, monotonic correlation between the free magnetic energy and the relative magnetic helicity in the studied regions. This correlation implies that magnetic helicity, besides free magnetic energy, may be an essential ingredient for major solar eruptions. Eruptive active regions appear well segregated from non-eruptive ones in both free energy and relative helicity with major (at least M-class) flares occurring in active regions with free energy and relative helicity exceeding 4x1031 erg and 2x1042 Mx^2, respectively. The helicity threshold agrees well with estimates of helicity contents of typical coronal mass ejections.

Authors: K.Tziotziou, M.K. Georgoulis & N-E. Raouafi
Projects: Hinode/SOT

Publication Status: ApJ Letters, in press
Last Modified: 2012-09-26 09:09
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Abstracts by Author
Energy and helicity budgets of solar quiet regions
Magnetic Energy and Helicity Budgets in NOAA AR 11158
The Magnetic Energy - Helicity Diagram of Solar Active Regions

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MSU Solar Physics.
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