Search Publications
Evidence of a long-term trend in total solar irradiance
Fröhlich, C.
Aims: During the solar minimum of 2008, the value of total solar irradiance at 1 AU (TSI) was more than 0.2 Wm-2 lower than during the last minimum in 1996, indicating for the first time a directly observed long-term change. On the other hand, chromospheric indices and hence solar UV irradiance do not exhibit a similar change.
Metho…
Relationship between wave processes in sunspots and quasi-periodic pulsations in active region flares
Nakariakov, V. M.; Sych, R.; Karlicky, M. +1 more
A phenomenological relationship between oscillations in a sunspot and quasi-periodic pulsations (QPP) in flaring energy releases at an active region (AR) above the sunspot is established. The analysis of the microwave emission recorded by the Nobeyama Radioheliograph at 17 GHz shows a gradual increase in the power of the 3-min oscillation train in…
A multi-periodic oscillatory event in a solar flare
Nakariakov, V. M.; Inglis, A. R.
Aims: Ratios of different significant periods found in the light curves of a solar flare exhibiting quasi-periodic pulsations (QPP) are used to distinguish between the possible physical mechanisms responsible for such periodic behaviour.
Methods: Time series data of the flaring event of 2002 July 3, observed via the Nobeyama Radioheliograph, N…
The onset of solar cycle 24. What global acoustic modes are telling us
Jiménez-Reyes, S. J.; García, R. A.; Pallé, P. L. +1 more
We study the response of the low-degree, solar p-mode frequencies to the unusually extended minimum of solar surface activity since 2007. A total of 4768 days of observations collected by the space-based, Sun-as-a-star helioseismic GOLF instrument are analyzed. A multi-step iterative maximum-likelihood fitting method is applied to subseries of 365…
Generation of highly energetic electrons at reconnection outflow shocks during solar flares
Mann, G.; Aurass, H.; Warmuth, A.
Context: During solar flares a large amount of energy is suddenly released and partly transferred into energetic electrons. They are of special interest since a substantial part of the energy released during a flare is deposited into the energetic electrons. RHESSI observations, e.g. of the 2003 October 28 solar event, show that 1036 el…
The solar chromosphere at high resolution with IBIS. II. Acoustic shocks in the quiet internetwork and the role of magnetic fields
Vecchio, A.; Cauzzi, G.; Reardon, K. P.
Context: The exact nature of the quiet solar chromosphere and especially its temporal variation, are still subjects of intense debate. One of the contentious issues is the possible role of the magnetic field in structuring the quieter solar regions.
Aims: We characterize the dynamics of the quiet inter-network chromosphere by studying the occu…
Quiet Sun mini-coronal mass ejections activated by supergranular flows
Innes, D. E.; Potts, H. E.; Attie, R. +1 more
Context: The atmosphere of the quiet Sun is controlled by photospheric flows sweeping up concentrations of mixed polarity magnetic field. Along supergranule boundaries and junctions, there is a strong correlation between magnetic flux and bright chromospheric and transition region emission.
Aims: The aim is to investigate the relationship betw…
Multi-wavelength observations and modelling of a canonical solar flare
Klimchuk, J. A.; Gallagher, P. T.; Milligan, R. O. +1 more
Aims: We investigate the temporal evolution of temperature, emission measure, energy loss, and velocity in a C-class solar flare from both observational and theoretical perspectives.
Methods: The properties of the flare were derived by following the systematic cooling of the plasma through the response functions of a number of instruments - th…
The possible role of vortex shedding in the excitation of kink-mode oscillations in the solar corona
Nakariakov, V. M.; Aschwanden, M. J.; van Doorsselaere, T.
We propose a model for the excitation of horizontally polarised transverse (kink) magnetoacoustic oscillations of solar coronal loops by upflows associated with coronal mass ejections. If the magnetic field in the plasma that is dragged in the vertical direction by the flow is parallel to the loop, the phenomenon of vortex shedding causes the appe…
Modelling shock drift acceleration of electrons at the reconnection outflow termination shock in solar flares. Observational constraints and parametric study
Mann, G.; Aurass, H.; Warmuth, A.
Context: The acceleration of electrons to nonthermal energies in solar flares is one of the main unsolved questions in solar physics. One possibility for producing these energetic electrons is acceleration at the reconnection outflow termination shock (TS).
Aims: By comparing theoretical results with observations of nonthermal electrons, we de…