The magnetic field in the solar atmosphere

Wiegelmann, T.; Thalmann, Julia K.; Solanki, S. K.

doi:10.1007/s00159-014-0078-7

Cited by 182 publications

(132 citation statements)

References 561 publications

(621 reference statements)

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“…The magnetic field in the quiet Sun is composed of the network (Sheeley 1967), internetwork (IN, Livingston & Harvey 1971, 1975, and the ephemeral regions (Harvey & Martin 1973). For an overview of the small-scale magnetic features, see Solanki (1993);de Wijn et al (2009);Priest (2014); Wiegelmann et al (2014).…”

Section: Introductionmentioning

confidence: 99%

Estimation of the Magnetic Flux Emergence Rate in the Quiet Sun from Sunrise Data

Smitha

Anusha

Solanki

et al. 2017

ApJS

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Small-scale internetwork (IN) features are thought to be the major source of fresh magnetic flux in the quiet Sun. During its first science flight in 2009, the balloon-borne observatory Sunrise captured images of the magnetic fields in the quiet Sun at a high spatial resolution. Using these data we measure the rate at which the IN features bring magnetic flux to the solar surface. In a previous paper it was found that the lowest magnetic flux in small-scale features detected using the Sunrise observations is 9 × 10 14 Mx. This is nearly an order of magnitude smaller than the smallest fluxes of features detected in observations from Hinode satellite. In this paper, we compute the flux emergence rate (FER) by accounting for such small fluxes, which was not possible before Sunrise. By tracking the features with fluxes in the range 10 15 − 10 18 Mx, we measure an FER of 1100 Mx cm −2 day −1 . The smaller features with fluxes ≤ 10 16 Mx are found to be the dominant contributors to the solar magnetic flux. The FER found here is an order of magnitude higher than the rate from the Hinode, obtained with a similar feature tracking technique. A wider comparison with the literature shows, however, that the exact technique of determining the rate of the appearance of new flux can lead to results that differ by up to two orders of magnitude, even when applied to similar data. The causes of this discrepancy are discussed and first qualitative explanations proposed.

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Section: Introductionmentioning

confidence: 99%

Estimation of the Magnetic Flux Emergence Rate in the Quiet Sun from Sunrise Data

Smitha

Anusha

Solanki

et al. 2017

ApJS

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“…According to the standard eruptive flare model (Carmichael 1964;Sturrock 1968;Hirayama 1974;Kopp & Pneuman 1976; see also reviews by Benz 2008;Fletcher et al 2011, and references therein), the energy to power solar flares is stored in the nonpotential coronal magnetic fields (e.g., Forbes 2000;Hudson 2011;Wiegelmann et al 2014). The mechanism that releases magnetic energy is known as magnetic reconnection.…”

Section: Introductionmentioning

confidence: 99%

Chromospheric evaporation flows and density changes deduced from Hinode/EIS during an M1.6 flare

Gömöry

Veronig

et al. 2016

A&A

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Aims. We study the response of the solar atmosphere during a GOES M1.6 flare using spectroscopic and imaging observations. In particular, we examine the evolution of the mass flows and electron density together with the energy input derived from hard X-ray (HXR) in the context of chromospheric evaporation.Methods. We analyzed high-cadence sit-and-stare observations acquired with the Hinode/EIS spectrometer in the Fe xiii 202.044 Å (log T = 6.2) and Fe xvi 262.980 Å (log T = 6.4) spectral lines to derive temporal variations of the line intensity, Doppler shifts, and electron density during the flare. We combined these data with HXR measurements acquired with RHESSI to derive the energy input to the lower atmosphere by flare-accelerated electrons.Results. During the flare impulsive phase, we observe no significant flows in the cooler Fe xiii line but strong upflows, up to 80-150 km s −1 , in the hotter Fe xvi line. The largest Doppler shifts observed in the Fe xvi line were co-temporal with the sharp intensity peak. The electron density obtained from a Fe xiii line pair ratio exhibited fast increase (within two minutes) from the pre-flare level of 5.01 × 10 9 cm −3 to 3.16 × 10 10 cm −3 during the flare peak. The nonthermal energy flux density deposited from the coronal acceleration site to the lower atmospheric layers during the flare peak was found to be 1.34 × 10 10 erg s −1 cm −2 for a low-energy cut-off that was estimated to be 16 keV. During the decline flare phase, we found a secondary intensity and density peak of lower amplitude that was preceded by upflows of ∼15 km s −1 that were detected in both lines. The flare was also accompanied by a filament eruption that was partly captured by the EIS observations. We derived Doppler velocities of 250-300 km s −1 for the upflowing filament material. Conclusions. The spectroscopic results for the flare peak are consistent with the scenario of explosive chromospheric evaporation, although a comparatively low value of the nonthermal energy flux density was determined for this phase of the flare. This outcome is discussed in the context of recent hydrodynamic simulations. It provides observational evidence that the response of the atmospheric plasma strongly depends on the properties of the electron beams responsible for the heating, in particular the steepness of the energy distribution. The secondary peak of line intensity and electron density detected during the decline phase is interpreted as a signature of flare loops being filled by expanding hot material that is due to chromospheric evaporation.

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“…Our simultaneous observations of jet activity with magnetic flux emergence, cancelation, and dynamic motions suggested by the small-scale time evolution provided by AIA and HMI suggest that such QS events may provide microinjections of helicity into the heliosphere, a self-similar attribute to large-scale helicity injections (Raouafi et al 2010;Wiegelmann et al 2014;Pariat et al 2015). That these events may provide non-negligible helicity to coronal heights and temperatures promotes the idea that QS jets cannot be ignored in the quest for a complete model of the TR.…”

Section: Discussionmentioning

confidence: 76%

Quiet-Sun Network Bright Point Phenomena With Sigmoidal Signatures

Chesny

Oluseyi

Orange³

et al. 2015

ApJ

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Ubiquitous solar atmospheric coronal and transition region bright points (BPs) are compact features overlying strong concentrations of magnetic flux. Here, we utilize high-cadence observations from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory to provide the first observations of extreme ultraviolet quietSun (QS) network BP activity associated with sigmoidal structuring. To our knowledge, this previously unresolved fine structure has never been associated with such small-scale QS events. This QS event precedes a bi-directional jet in a compact, low-energy, and low-temperature environment, where evidence is found in support of the typical fan-spine magnetic field topology. As in active regions and micro-sigmoids, the sigmoidal arcade is likely formed via tether-cutting reconnection and precedes peak intensity enhancements and eruptive activity. Our QS BP sigmoid provides a new class of small-scale structuring exhibiting self-organized criticality that highlights a multiscaled self-similarity between large-scale, high-temperature coronal fields and the small-scale, lower-temperature QS network. Finally, our QS BP sigmoid elevates arguments for coronal heating contributions from cooler atmospheric layers, as this class of structure may provide evidence favoring mass, energy, and helicity injections into the heliosphere.

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The magnetic field in the solar atmosphere

Cited by 182 publications

References 561 publications

Estimation of the Magnetic Flux Emergence Rate in the Quiet Sun from Sunrise Data

Estimation of the Magnetic Flux Emergence Rate in the Quiet Sun from Sunrise Data

Chromospheric evaporation flows and density changes deduced from Hinode/EIS during an M1.6 flare

Quiet-Sun Network Bright Point Phenomena With Sigmoidal Signatures

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