Longitude

About: Longitude is a research topic. Over the lifetime, 2260 publications have been published within this topic receiving 54988 citations. The topic is also known as: angle of longitude.

Longitudinal and temporal variations of sunspot regions and coronal holes during Cycle 21

Abstract: The relationship between sunspot activity in heliographic longitude and coronal holes is investigated for the period corresponding to Cycle 21 (Carrington rotations 1623–1779). The major result is that, based on He i 10830 A data, a strong inverse association is found between the longitudinal positions of sunspot groups and the size and number of coronal holes (especially, the equatorial extensions of polar holes). Frequencies of coincidences in longitude were determined for both types of activity and the evolution of coronal holes over Cycle 21 is depicted in the form of a ‘butterfly diagram’ displaying their latitudinal and longitudinal extents. A tabular listing identifies average longitude and persistence of sunspot active longitudes.

Motions in Sunspots Like Torsional Oscillations

Abstract: To study the rotation of sunspots, we selected the observational data for one group, namely for group which crossed the central meridian in October 4, 1974. This group was located in the southern hemisphere of the Sun (φ ≈ −60). It consisted of two large sunspots: preceding N-polarity spot and following S-polarity spot were separated by ∆L ≈ 90 in longitude. The magnetic field strength of both sunspots was approximately the same, i.e. about 2500G.

Earthquake Early Warning System Using Ncheck and Hard-Shared Orthogonal Multitarget Regression on Deep Learning

Abstract: Realizing an effective earthquake early warning system (EEWS) in the case of extensive regions and noisy signals is challenging, particularly in East Java, Indonesia. This letter proposes the rapid detection of the p-wave arrival and determination of the earthquake's hypocenter and magnitude using deep learning. The Ncheck algorithm is used for noise handling for picking the p-arrival on a multistation waveform as a form of picking target window prediction (PTWP). Then, multitarget regression (MTR) with a hard-shared orthogonal optimization model is proposed for earthquake parameter determination. The data sets used contained data of earthquakes recorded at three stations from the Indonesian seismic network in East Java; 2009-2017 data were used for training and validation, and 2019 data were used for real-time testing. The results show that the PTWP for picking p-arrival has a mean absolute error (MAE) of 0.12 s, and the MTR for earthquake magnitude, longitude, latitude, depth, and origin time detection shows MAEs of 0.21 M, 9.44, 18.72, 27.81 km, and 2.78 s, respectively.

Estimate of wind stressed sea level excitation of the Earth's annual wobble

Abstract: Summary. This article estimates the contribution to the Earth's annual wobble caused by the wind stressed non-isostatic sea level variations in the oceans. Since there is a lack of data on these sea level changes, an analytic approach is taken. An ocean basin is assumed to be bounded by two meridians of longitude and two parallels of latitude, and is symmetric about the equator. A simple zonal wind stress profile based on observed data represents the seasonal changes in each hemisphere with a simple annual cosine variation. The one layer barotropic ocean has a frictionally controlled boundary layer giving rise to a western boundary current. From the equations of motion a stream function and vorticity equation are developed. The ocean is assumed to be always in adjustment to the wind stress forcing so that the steady state solution yields the velocity and height fields. Model parameters are adjusted so that these sea level changes correspond to estimates of nonisostatic sea level changes. The expression for the annual height field changes caused by the wind stress forcing is substituted into the equations governing the wobble excitation. From the resulting expression it is seen that for an ocean basin and wind regime symmetric about the equator, the contributions to the excitation of wobble from the northern and southern oceans add, while the contributions to the length of day cancel. The pole of excitation for the resultant of all oceans moves along an ellipse of eccentricity unity (line segment), aligned nearly along the Greenwich meridian, with semi-major axes of 19 cm, and is farthest from the pole of reference along 11° E longitude in mid-February. This indicates that the major contribution to the sea level excitation comes from the set up in the western Pacific. The positive annual frequency vector is calculated to be (1.2–0.8i)×10−8 rad. Comparisons with the results of Wilson & Haubrich (1976a) show that this wind stressed sea level excitation of wobble is of the phase and probable magnitude to significantly reduce the discrepancy between the astronomically observed excitation and the calculated geophysical excitations due to air mass redistribution, continental water storage and mountain torque.