ABSTRACT
In this study, we, for the first time, compiled all publicly available annually or biannually resolved 14 C records, which fully covers 7 grand solar minima at an annual and bi-annual resolution. Our results from 7 grand solar minima showed a clear relationship between the rate of increase (decrease) in solar activity levels and how long the onset (termination) of the grand solar minima will last. Additionally, we show a weaker relationship between the durations of onsets and terminations and between the rate of increase and decrease of solar activity levels. Our results also suggest there might be two or more types of grand solar minima.
ABSTRACT
Through variations in its magnetic activity at different timescales, the Sun strongly influences the space weather conditions throughout the heliosphere. The most known solar activity variation is the Schwabe Cycle, also known as the Sunspot Cycle (SCs), period of which ranges from 9 to 13 years. The Sun also shows shorter quasi-periodic variations, such as the quasi-biennial oscillations (QBOs), superposed on the SCs. The QBOs are thought to be a global phenomena extending from the subsurface layers of the Sun to Earth and throughout the Heliosphere with a period generally between 1.3 and 1.6 years. In this study, we, for the first time, detected signals with periods ranging from 1.3 to 1.6 years in Earth's magnetosphere, which can be associated with the solar QBOs, using data from multiple GOES missions. The QBO-like signals detected in Earths Magnetopshere are thought to be propagated via the solar wind from the solar surface.
ABSTRACT
Galactic Cosmic Rays (GCRs) are charged particles, originating from galactic and/or extra-galactic Supernova Remnants (SNR), that continuously permeate the Heliosphere. The GCRs are modulated in the heliosphere by convection by solar wind (SW), drift via gradients and curvatures in the Heliospheric Magnetic Field (HMF), diffusion from fluctuations in the HMF, and adiabatic cooling in the expanding SW. An improved understanding of their modulation is imperative as studies on the variations in solar activity levels and solar eruptions in the past rely heavily on the relationship between their modulation and formation of the secondary particles in the Earth's atmosphere. Here, for the first time, we utilize an AI method, Light Gradient Boosting Machines (LightGBM), to investigate the nonlinear interplay among the modulation processes in different timescales. Our study indicates that the nonlinear interplay among the mechanisms responsible for the GCR modulation in the inner heliosphere are not limited to the scenario of "drift-dominated solar minimum" versus "diffusion-dominated solar maximum", instead they have dynamic behavior displaying variations in time and in timescales. This study also demonstrates the value of using AI methods to investigate non-linear physical processes in Space Physics in the era of big data.
ABSTRACT
Superflares are large explosive events on stellar surfaces one to six orders-of-magnitude larger than the largest flares observed on the Sun throughout the space age. Due to the huge amount of energy released in these superflares, it has been speculated if the underlying mechanism is the same as for solar flares, which are caused by magnetic reconnection in the solar corona. Here, we analyse observations made with the LAMOST telescope of 5,648 solar-like stars, including 48 superflare stars. These observations show that superflare stars are generally characterized by larger chromospheric emissions than other stars, including the Sun. However, superflare stars with activity levels lower than, or comparable to, the Sun do exist, suggesting that solar flares and superflares most likely share the same origin. The very large ensemble of solar-like stars included in this study enables detailed and robust estimates of the relation between chromospheric activity and the occurrence of superflares.
