Solar Cycle Indices from the Photosphere to the Corona: Measurements and Underlying Physics

Ermolli, I.; Shibasaki, Κ.; Tlatov, A. G.; Driel-Gesztelyi, L. van

doi:10.1007/s11214-014-0089-8

Cited by 56 publications

(29 citation statements)

References 140 publications

(126 reference statements)

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“…Nowadays, space‐based instrumentation, such as those onboard HINODE (Kosugi et al ), SDO (Pesnell et al ), and IRIS (De Pontieu et al ), provides continuous monitoring of the Sun at sub‐arcsecond spatial resolution over different spectral ranges. Such measurements complement multi‐decadal full‐disk observations of the photospheric and chromospheric magnetic flux (e.g., Ermolli et al , and references therein). Starting in 2019, the 4‐m Daniel K. Inouye Solar Telescope (DKIST, see Tritschler et al 2016) will observe the solar atmosphere at unprecedented spatial resolution and, by combining state‐of‐the‐art instrumentation, will retrieve the solar magnetic field from the photosphere to the corona.…”

Section: Introductionmentioning

confidence: 60%

The variability of magnetic activity in solar‐type stars

et al. 2017

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This article reviews the current knowledge and status of investigations on the variable magnetic activity of cool stars. We discuss the Sun in the context of solar-type stars, highlighting peculiarities and common features in terms of its magnetic activity and variability over different time scales. We examine how both theory and observations are providing new clues about the main physical processes that generate magnetic fields in the interior of cool stars, as well as about those that lead to evolving stellar surface magnetism and varying chromospheric and coronal phenomena. We then proceed to discuss the relations between stellar age, rotation, and activity throughout the evolution of cool stars. Finally, we touch upon the importance of understanding stellar magnetism also in view of its effect on planetary environments.

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Section: Introductionmentioning

confidence: 60%

The variability of magnetic activity in solar‐type stars

et al. 2017

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“…Earlier studies (see Rybanský et al 2001;Mavromichalaki et al 2002Mavromichalaki et al , 2005Minarovjech et al 2007;Ermolli et al 2014) have shown that the intensity of the green corona is highly correlated with other solar activity indicators as all of them are intrinsically inter-linked through solar magnetism. So, the MCI is applied here as an indicator to describe the temporal variability of solar magnetic activity.…”

Section: Phase Relationship Between Coronal Rotation and Solar Activitymentioning

confidence: 99%

Systematic regularity of solar coronal rotation during the time interval 1939–2019

Deng

Zhang

Deng

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Temporal variation of the solar coronal rotation appears to be very complex and its relevances to the eleven-year solar activity cycle are still unclear. Using the modified coronal index for the time interval from 1939 January 1 to 2019 May 31, the systematic regularities of the solar coronal rotation are investigated. Our main findings are as follows: (1) from a global point of view, the synodic coronal rotation period with a value of 27.5 days is the only significant period at the periodic scales shorter than 64 days; (2) the coronal rotation period exhibit an obviously decreasing trend during the considered time interval, implying the solar corona accelerates its global rotation rate in the long run; (3) there exist significant periods of 3.25, 6.13, 9.53, and 11.13 years in the period length of the coronal rotation, providing an evidence that the coronal rotation should be connected with the quasi-biennial oscillation, the eleven-year solar cycle, and the 22-year Hale cycle (or the magnetic activity reversal); and (4) the phase relationship between the coronal rotation period and the solar magnetic activity is not only time-dependent but also frequency-dependent. For a small range around the 11-year cycle band, there is a systematic trend in the phase, and the small mismatch in this band brings out the phase to drift. The possible mechanism for the above analysis results is discussed.

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“…In the next section we shall compare it directly to thermospheric density observations. There exist many UV proxies (Ermolli et al 2014), each of which preferentially describes a spectral band or a class of solar features. Those proxies which have been specifically recommended for drag modelling (e.g.…”

Section: Comparison With Solar Proxiesmentioning

confidence: 99%

The 30 cm radio flux as a solar proxy for thermosphere density modelling

Wit

Bruinsma²

2017

J. Space Weather Space Clim.

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The 10.7 cm radio flux (F10.7) is widely used as a proxy for solar UV forcing of the upper atmosphere. However, radio emissions at other centimetric wavelengths have been routinely monitored since the 1950 s, thereby offering prospects for building proxies that may be better tailored to space weather needs. Here we advocate the 30 cm flux (F30) as a proxy that is more sensitive than F10.7 to longer wavelengths in the UV and show that it improves the response of the thermospheric density to solar forcing, as modelled with DTM (Drag Temperature Model). In particular, the model bias drops on average by 0-20% when replacing F10.7 by F30; it is also more stable (the standard deviation of the bias is 15-40% smaller) and the density variation at the the solar rotation period is reproduced with a 35-50% smaller error. We compare F30 to other solar proxies and discuss its assets and limitations.

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Solar Cycle Indices from the Photosphere to the Corona: Measurements and Underlying Physics

Cited by 56 publications

References 140 publications

The variability of magnetic activity in solar‐type stars

The variability of magnetic activity in solar‐type stars

Systematic regularity of solar coronal rotation during the time interval 1939–2019

The 30 cm radio flux as a solar proxy for thermosphere density modelling

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