Search results for "Earth's magnetic field"
showing 10 items of 19 documents
Towards Understanding the Interconnection between Celestial Pole Motion and Earth’s Magnetic Field Using Space Geodetic Techniques
2021
The understanding of forced temporal variations in celestial pole motion (CPM) could bring us significantly closer to meeting the accuracy goals pursued by the Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG), i.e., 1 mm accuracy and 0.1 mm/year stability on global scales in terms of the Earth orientation parameters. Besides astronomical forcing, CPM excitation depends on the processes in the fluid core and the core–mantle boundary. The same processes are responsible for the variations in the geomagnetic field (GMF). Several investigations were conducted during the last decade to find a possible interconnection of GMF changes with the length of day (…
Understanding the Origins of Problem Geomagnetic Storms Associated with "Stealth" Coronal Mass Ejections.
2021
Geomagnetic storms are an important aspect of space weather and can result in significant impacts on space- and ground-based assets. The majority of strong storms are associated with the passage of interplanetary coronal mass ejections (ICMEs) in the near-Earth environment. In many cases, these ICMEs can be traced back unambiguously to a specific coronal mass ejection (CME) and solar activity on the frontside of the Sun. Hence, predicting the arrival of ICMEs at Earth from routine observations of CMEs and solar activity currently makes a major contribution to the forecasting of geomagnetic storms. However, it is clear that some ICMEs, which may also cause enhanced geomagnetic activity, cann…
Polarization-driven spin precession of mesospheric sodium atoms
2018
We report experimental results on the first on-sky observation of atomic spin precession of mesospheric sodium driven by polarization modulation of a continuous-wave laser. The magnetic resonance was remotely detected from the ground by observing the enhancement of induced fluorescence when the driving frequency approached the precession frequency of sodium in the mesosphere, between 85 km and 100 km altitude. The experiment was performed at La Palma, and the uncertainty in the measured Larmor frequency ($\approx$260 kHz) corresponded to an error in the geomagnetic field of 0.4 mG. The results are consistent with geomagnetic field models and with the theory of light-atom interaction in the …
Unusually high frequency natural VLF radio emissions observed during daytime in Northern Finland
2016
Geomagnetic field variations and electromagnetic waves of different frequencies are ever present in the Earth's environment in which the Earth's fauna and flora have evolved and live. These waves are a very useful tool for studying and exploring the physics of plasma processes occurring in the magnetosphere and ionosphere. Here we present ground-based observations of natural electromagnetic emissions of magnetospheric origin at very low frequency (VLF, 3–30 kHz), which are neither heard nor seen in their spectrograms because they are hidden by strong impulsive signals (sferics) originating in lightning discharges. After filtering out the sferics, peculiar emissions are revealed in these dig…
A Multi-Position Calibration Method for Consumer-Grade Accelerometers, Gyroscopes, and Magnetometers to Field Conditions
2017
This paper presents a calibration method for consumer-grade accelerometers, gyroscopes, and magnetometers. Considering the calibration of consumer-grade sensors, it is essential that no specialized equipment is required to create reference signals. In addition, the less is required from the reference signals, the more suitable the method is on the field. In the proposed method, the novelty in the calibration of the gyroscopes lies in the exploitation of only the known net rotations between the positions in a multi-position calibration. For accelerometers and magnetometers, the innovation is that the direction of reference signals, the gravity and the magnetic field of the Earth, are estimat…
Solar and interplanetary triggers of the largest Dst variations of the solar cycle 23
2012
Abstract We present the results of an investigation from the Sun to the Earth of the sequence of events that caused major Dst decreases (Δ Dst ≤ – 100 nT during 1 h) that occurred during 1996–2005. These events are expected to be better related to geomagnetic induced current (GIC) events than those events where any geomagnetic index is far from its quiet time value. At least one full halo CME with a speed on the plane of sky above 900 km/s participates in every studied event. The seven events were triggered by interplanetary signatures, which arise as a consequence of interaction among different solar ejections. The interaction arises at different stages from the solar surface, between segm…
Sensitivity of the Cherenkov Telescope Array to emission from the gamma-ray counterparts of neutrino events
2021
We investigate the possibility of detection of the VHE gamma-ray counterparts to the neutrino astrophysical sources within the Neutrino Target of Opportunity (NToO) program of CTA using the populations simulated by the FIRESONG software to resemble the diffuse astrophysical neutrino flux measured by IceCube. We derive the detection probability for different zenith angles and geomagnetic field configurations. The difference in detectability of sources between CTA-North and CTA-South for the average geomagnetic field is not substantial. We investigate the effect of a higher night-sky background and the preliminary CTA Alpha layout on the detection probability.
Observation of the cosmic-ray shadow of the Moon with IceCube
2013
We report on the observation of a significant deficit of cosmic rays from the direction of the Moon with the IceCube detector. The study of this "Moon shadow" is used to characterize the angular resolution and absolute pointing capabilities of the detector. The detection is based on data taken in two periods before the completion of the detector: between April 2008 and May 2009, when IceCube operated in a partial configuration with 40 detector strings deployed in the South Pole ice, and between May 2009 and May 2010 when the detector operated with 59 strings. Using two independent analysis methods, the Moon shadow has been observed to high significance (> 6 sigma) in both detector config…
The First Terrestrial Electron Beam Observed by the Atmosphere‐Space Interactions Monitor
2019
We report the first Terrestrial Electron Beam detected by the Atmosphere‐Space Interactions Monitor. It happened on 16 September 2018. The Atmosphere‐Space Interactions Monitor Modular X and Gamma ray Sensor recorded a 2 ms long event, with a softer spectrum than typically recorded for Terrestrial Gamma ray Flashes (TGFs). The lightning discharge associated to this event was found in the World Wide Lightning Location Network data, close to the northern footpoint of the magnetic field line that intercepts the International Space Station location. Imaging from a GOES‐R geostationary satellite shows that the source TGF was produced close to an overshooting top of a thunderstorm. Monte‐Carlo si…
Production and detection of atomic hexadecapole at Earth’s magnetic field
2007
We report a novel method that allows selective creation and detection of a macroscopic long lived hexadecapole polarization in the F = 2 ground state of 87Rb atoms at Earth's magnetic field (510 mG).