47 research outputs found
Near-surface Azimuthal Magnetic Fields and Solar Activity Cycles
Variations of the azimuthal magnetic fields of the Sun in the 23-25 activity
cycles of the activity cycles are considered. To identify azimuthal magnetic
fields, the analysis of daily observations of LOS magnetic fields from the
regions near the solar limb was performed. It is shown that with a sufficiently
large averaging of the data, large-scale structures are distinguished that can
be interpreted by horizontal magnetic fields directed along the East-West line.
Azimuthal magnetic fields are visible both in the low-latitude zone and at high
latitudes. Azimuthal fields at the same latitudes have opposite directions in
the northern and southern hemispheres, and also change sign in even and odd
cycles of activity. The mechanism of formation of global azimuthal magnetic
fields and their role in the cycle of solar activity is discussed. The
near-surface azimuthal magnetic field is closely related to the activity cycle.
Apparently, the azimuthal field is formed from U-shaped flux tubes of active
regions (AR). Due to the presence of the tilt angle AR during differential
rotation, the subsurface magnetic fields are pulled in the azimuthal direction.
The role of azimuthal magnetic fields in solar activity cycles is considered. A
scheme for generating a magnetic field according to a scheme different from
Babcock-Leighton dynamo models is proposed.Comment: 10 pages, 9 figure
The Minimum of Solar Cycle 23: As Deep as It Could Be?
In this work we introduce a new way of binning sunspot group data with the
purpose of better understanding the impact of the solar cycle on sunspot
properties and how this defined the characteristics of the extended minimum of
cycle 23. Our approach assumes that the statistical properties of sunspots are
completely determined by the strength of the underlying large-scale field and
have no additional time dependencies. We use the amplitude of the cycle at any
given moment (something we refer to as activity level) as a proxy for the
strength of this deep-seated magnetic field.
We find that the sunspot size distribution is composed of two populations:
one population of groups and active regions and a second population of pores
and ephemeral regions. When fits are performed at periods of different activity
level, only the statistical properties of the former population, the active
regions, is found to vary.
Finally, we study the relative contribution of each component (small-scale
versus large-scale) to solar magnetism. We find that when hemispheres are
treated separately, almost every one of the past 12 solar minima reaches a
point where the main contribution to magnetism comes from the small-scale
component. However, due to asymmetries in cycle phase, this state is very
rarely reached by both hemispheres at the same time. From this we infer that
even though each hemisphere did reach the magnetic baseline, from a
heliospheric point of view the minimum of cycle 23 was not as deep as it could
have been
MASTER prompt and follow-up GRB observations
There are the results of gamma-ray bursts observations obtained using the
MASTER robotic telescope in 2007 - 2009. We observed 20 error-boxes of
gamma-ray bursts this period.The limits on their optical brightnesses have been
derived. There are 5 prompt observations among them, obtained at our very wide
field cameras. Also we present the results of the earliest observations of the
optical emission of the gamma-ray bursts GRB 050824 and GRB 060926.Comment: 10 pages, 2 figure