scholarly journals Averaging and sampling for magnetic-observatory hourly data

2010 ◽  
Vol 28 (11) ◽  
pp. 2079-2096 ◽  
Author(s):  
J. J. Love ◽  
V. C. Tsai ◽  
J. L. Gannon
Keyword(s):  
Low Frequency ◽  
Magnetic Observatory ◽  
Geomagnetic Variation ◽  
Field Variation ◽  
Brick Wall ◽  
Monthly Means ◽  
Low Latitude ◽  
Amplitude Distortion ◽  
Hourly Data ◽  
Average Sample

Abstract. A time and frequency-domain analysis is made of the effects of averaging and sampling methods used for constructing magnetic-observatory hourly data values. Using 1-min data as a proxy for continuous, geomagnetic variation, we construct synthetic hourly values of two standard types: instantaneous "spot" measurements and simple 1-h "boxcar" averages. We compare these average-sample types with others: 2-h average, Gaussian, and "brick-wall" low-frequency-pass. Hourly spot measurements provide a statistically unbiased representation of the amplitude range of geomagnetic-field variation, but as a representation of continuous field variation over time, they are significantly affected by aliasing, especially at high latitudes. The 1-h, 2-h, and Gaussian average-samples are affected by a combination of amplitude distortion and aliasing. Brick-wall values are not affected by either amplitude distortion or aliasing, but constructing them is, in an operational setting, relatively more difficult than it is for other average-sample types. It is noteworthy that 1-h average-samples, the present standard for observatory hourly data, have properties similar to Gaussian average-samples that have been optimized for a minimum residual sum of amplitude distortion and aliasing. For 1-h average-samples from medium and low-latitude observatories, the average of the combination of amplitude distortion and aliasing is less than the 5.0 nT accuracy standard established by Intermagnet for modern 1-min data. For medium and low-latitude observatories, average differences between monthly means constructed from 1-min data and monthly means constructed from any of the hourly average-sample types considered here are less than the 1.0 nT resolution of standard databases. We recommend that observatories and World Data Centers continue the standard practice of reporting simple 1-h-average hourly values.

scholarly journals One second vector and scalar magnetic measurements at low latitude observatory, CPL

2017 ◽  
Author(s):  
Phani Chandrasekhar Nelapatla ◽  
Sai Vijay Kumar Potharaju ◽  
Kusumita Arora ◽  
Chandra Shakhar Rao Kasuba ◽  
Leonid Rakhlin ◽  
...  
Keyword(s):  
Real Time ◽  
Magnetic Measurements ◽  
Low Frequency ◽  
Magnetic Data ◽  
Magnetic Observatory ◽  
Fluxgate Magnetometer ◽  
Main Concern ◽  
Low Latitude ◽  
Time Space ◽  
New Instrument

Abstract. There is increasing demand from the global geomagnetic community for the recording of 1 second vector and scalar magnetic datain lieu of the traditional of the 1 minute data, as the 1 second magnetic data would be more compatible with measurements made from low-earth orbiting satellites and the increased detectability threshold, would contribute to: (i) understanding the global scale ultra-low frequency (ULF) waves, sudden impulses and other processes in the ionosphere & magnetosphere: (ii) development of real-time space weather forecasts. The combination of ground and satellite data opens a new pathway in understanding many underlying physical processes in the lower-middle atmospheric dynamics, which has not been accurately understood so far. The International Real-time Magnetic ObservatoryNetwork (INTERMAGNET)observatories (IMO-s) have taken a lead in this direction and many IMO-s now produce both 1 minute and 1 second data. Being affordable, rugged, compact as well as having low power consumption, fluxgate magnetometers are the staple vector sensors of IMO-s.The increased order of noise in these sensors with increasing frequencies, is the main concern and work has been going on for the last decade towards development of suitable instruments (Courtillot and Chulliat, 2008; Korepanov et al. 2006, 2009; Pedersen and Merenyi, 2016 and references therein, Dobrodnyak, 2014; Logvinov, 2014) and techniques for the evaluation and elimination of noise from the data is also being pursued (Turbitt et al. 2013). At the new Magnetic Observatory of CSIR-NGRI in Choutuppal (CPL) campus, 1 second magnetic measurements commenced in the year 2016 using the newly developed Observatory grade 1 second fluxgate magnetometer, GEOMAG-02MO, from GEOMAGNET Ukraine and the Overhauser Proton Precession Magnetometer along with the data acquisition system, MAGREC-4B. The processes of commissioning of this setup in low-latitude conditions, with the aim to finally produce 1 second definitive data (the standards of which are still under discussion with INTERMAGNET) and the characteristics of the data from this new instrument are presented in this work.

VLF/LF (Very Low Frequency/Low Frequency) Reflection Properties of the Low Latitude Ionosphere

1988 ◽  
Author(s):  
Wayne I. Klemetti ◽  
Paul A. Kossey ◽  
John E. Rasmussen ◽  
Maria Sueli Da Silveira Macedo Moura
Keyword(s):  
Low Frequency ◽  
Low Latitude ◽  
Very Low Frequency ◽  
Low Latitude Ionosphere

Polarization pattern of low-frequency geomagnetic field fluctuations (0.8-3.6 mHz) at high and low latitude

1999 ◽  
Vol 104 (A1) ◽  
pp. 305-310 ◽  
Author(s):  
S. Lepidi ◽  
P. Francia ◽  
U. Villante ◽  
L. J. Lanzerotti ◽  
A. Meloni
Keyword(s):  
Geomagnetic Field ◽  
Low Frequency ◽  
Polarization Pattern ◽  
Low Latitude ◽  
Field Fluctuations

scholarly journals Remote auroral activity detection and modeling using low frequency transmitter signal reception at a midlatitude site

2010 ◽  
Vol 28 (9) ◽  
pp. 1807-1811 ◽  
Author(s):  
E. D. Schmitter
Keyword(s):  
Power Systems ◽  
Low Frequency ◽  
Solar Energetic Particle ◽  
Auroral Oval ◽  
Activity Level ◽  
Propagation Model ◽  
Low Latitude ◽  
Activity Data ◽  
Auroral Activity ◽  
Local Intensity

Abstract. The low frequency propagation conditions along the path from Iceland to Germany (52° N 8° E) using the NRK/TFK 37.5 kHz transmitter (63.9° N 22.5° W) prove as an easy to monitor and reliable proxy for north auroral activity. Signal processing using wavelet decomposition allows for quantitative activity level estimations. Calibration is based upon NOAA POES auroral activity data. Using an auroral oval model for the local intensity distribution of solar energetic particle precipitation and a wave propagation model ionospheric D-layer height decreases along the path can be derived. This in turn gives a hint to the low latitude extension and intensity of the auroral electrojet currents that can be responsible for communication and power systems failures.

I. On the solar-diurnal variation of the magnetic declination at Pekin

1860 ◽  
Vol 10 ◽  
pp. 360-374
Keyword(s):  
Diurnal Variation ◽  
First Year ◽  
Magnetic Observatory ◽  
Magnetic Element ◽  
Monthly Means ◽  
The North ◽  
The Hours ◽  
The Mean ◽  
The Times ◽  
North End

When the first year of hourly observations of the declination, January 1 to December 31st, 1841, was received at Woolwich from the Magnetic Observatory at Hobarton, and when means had been taken of the readings of the collimator-scale at the several hours in each month, and these monthly means had been collected into an­nual means, it was found that the mean daily motion of the declina­tion magnet at Hobarton presented, as one of its most conspicuous and well-marked features, a double progression in the twenty-four hours, moving twice from west to east, and twice from east to west; the phases of this diurnal variation were, that the north end of the magnet moved progressively from west to east in the hours of the forenoon, and from east to west in the hours of the afternoon ; and again from west to east during the early hours of the night, return­ing from east to west during the later hours of the night: the two easterly extremes were attained at nearly homonymous hours of the day and night, as were also the two westerly extremes; the ampli­tudes of the arcs traversed during the hours of the day were con­siderably greater than those traversed during the hours of the night. When, in like manner, the first year of hourly observations, July 1st, 1842, to June 30th, 1843, was received from the Toronto Ob­servatory, and the mean diurnal march of the declination magnet was examined, it was found to exhibit phenomena in striking corre­spondence with those at Hobarton. At Toronto also a double pro­gression presented itself, of which the easterly extremes were attained at nearly homonymous hours, as were also the westerly; whilst the hours of extreme elongation were nearly the same (solar) hours at the two stations, but with this distinction, that the hours at which the north end of the magnet reached its extreme easterly elongation at Hobarton were the same, or nearly the same, as those at which it reached its extreme westerly elongation at Toronto, and vice verâ Pursuing, therefore, the ordinary mode of designating the direction of the declination by the north end of the magnet in the southern as well as in the northern hemisphere, the diurnal motion of the magnet may be said to be in opposite directions at Hobarton and Toronto; but if (in correspondence with our mode of speaking in regard to another magnetic element, the Inclination) the south end of the magnet is employed to designate the direction of the motion in the southern hemisphere, and the north end in the northern hemisphere, the apparent contrariety disappears, and the directions, as well as the times of the turning hours, are approximately the same at both stations.

scholarly journals Low frequency geomagnetic field fluctuations at low latitude during the passage of a higher pressure solar wind region

1997 ◽  
Vol 15 (6) ◽  
pp. 656-661
Author(s):  
U. Villante ◽  
P. Francia
Keyword(s):  
Solar Wind ◽  
Geomagnetic Field ◽  
Low Frequency ◽  
Frequency Range ◽  
Low Latitude ◽  
Wind Region ◽  
Spectral Peaks ◽  
Field Fluctuations ◽  
Term Analysis

Abstract. The passage of a higher pressure solar wind region at the Earth's orbit marked the onset of low latitude (L=1.6) fluctuations in the frequency range (0.8–5.5 mHz) for both the horizontal geomagnetic field components. Spectral peaks mostly occur at the same frequencies as the spectral enhancements which appeared in the long term analysis of experimental measurements from the same station and were tentatively interpreted in terms of ground signatures of global magnetospheric modes. A comparison with simultaneous observations discussed by previous investigations allows us to conclude that the same set of frequencies is enhanced in a wide portion of the Earth's magnetosphere.

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